Start out the battle by going forward and capturing the east and west bases near your location. Once you've captured both, head across the bridges and then enter the Eight Gates Formation through the designated gate. When you're inside of the Formation, follow what Xu Shu says and start following the path that is shown to you.
You'll encounter some officers along the way, and then Cao Ren in the very last area of the Formation. Once you have defeated the Formation, you'll need to defeat the rest of the officers on the map. Zhang He will be close to the Formation, but Yue Jin and Li Dian will likely be inside of your main camp to the south.
With all of Cao Cao's troops gone, the only thing left to do is go to where the Sleeping Dragon is located. When you cross the bridge marked on your map, Yueying and some other troops will appear to stop you. Defeating her will open the way to where the Sleeping Dragon resides, and the battle will end once you get there.